Study of the postembryonic development of Idaea inquinata under different abiotic factors

Abstract

Abstract We investigated the biology of Idaea inquinata (Scopoli) (Lepidoptera Geometridae), the rusty wave moth, to determine the number and duration of larval instars and the duration of the pupal stage. The study was conducted at 21, 26, 29, and 34 ± 1 °C; for each temperature tests were conducted at 35 and 70 ± 5% relative humidity (RH), with a photoperiod of 16:8 (light:dark). At 35% RH, five larval instars were observed at 26, 29, and 34 °C, whereas eight instars were found at 21 °C. At 21 °C and 70% RH, only one larva pupated after the fifth instar, two completed the sixth instar and one reached the seventh instar. At 21 °C and 35% RH an increase of mortality and in the number of larval instars was observed; the few larvae that reached the tenth instar did not survive. The shortest larval developmental periods were observed at 26 and 29 °C at 70% RH and were 31.9 ± 2.26 and 30.6 ± 3.12 days respectively. The longest developmental period was recorded at 21 °C and 35% RH, and was 172.5 ± 16.26 days. The pupal stage was longer at 21 °C at 35 and 70% RH, and lasted 22.5 ± 2.12 and 22 ± 3.65 days respectively. In all other conditions, the pupal periods lasted from 9 to 10 days. The highest adult emergence was observed at 26 and 29 °C at 70% RH and corresponded to 90% and 83% respectively. I. inquinata did not complete development at 34 °C and 35% RH. At 34 °C and 70% RH, only 13% of the specimens reached the adult stage. At 26 °C and 35% RH there was 66% adult emergence but this declined to 30% at 29°C and 35% RH. Percentage of adult emergence at 21 °C and 35% and 70% RH were 6 and 13% respectively. Considering the reduction in adult emergence at 21 °C, we recommend that a temperature of 18° C is maintained in air conditioned warehouses for the storage of dried medicinal plants to prevent I. inquinata infestations